Field of the Invention
This invention relates to an actuator device and more particularly to a high pressure rotary vane actuator device wherein the vanes of the rotor are moved by fluid under high pressure.
Rotary vane actuators are used as an essential part of some robotic devices. When connected with a series of servo-motors and drives and using the proper electromechanical principles and devices, such vane actuators are essential to the entire robotic device. For example, some robotic arms, such Alstom Automation Schilling Robotics"" Orion manipulator have as many as seven joints. Such robotic arms employ a ported rotary vane actuator having a like number of ports. Each joint is connected to one or more ports and a valve for moving each joint separately and/or conjunctively depending on the user""s desires.
An important use of such robotic arms is for submersible exploration. For example, exploring to find oil or other minerals and deposits requires exploration of undersea areas. A robotic arm is attached to either a manned or unmanned submersible. The sea bottom can then be explored as if a man were walking on the ocean bottom instead of being safely on a ship or in the submersible. The robotic arm must be able to work in difficult and even treacherous environments whose is ecology is highly sensitive to pollution, especially hydro carbons found in oil leaks.
In order for these robotic arms to function properly, the rotor is rotated by fluid under extremely high pressure. The rotating fluid is typically under pressures of 3000 pounds per square inch (PSI) ambient as is known for such devices. The adverse environmental conditions also create working difficulties. For example pressures at up to 13,000 PSI gage on the ocean floor are experienced during operation of the robotic arms.
As noted above, the robotic arm typically works in environments having sensitive ecology, which are subject to close political scrutiny. It is consequently unacceptable for the rotating fluid to leak into such environments. Great care must be taken to ensure that there is no fluid leakage even under the extreme conditions presented by environments such as the North Sea, for example. Also, the pressure within the actuator must likewise not give rise to any leakage.
Additionally, any leakage of fluid in the actuator will cause the robotic device to be moved freely without operator activation. When there is a drop in fluid pressure due to such leakage there will be play in the affected joint. This means that the arm joint can move by the forces of its surroundings. Given the gravitational forces acting upon the robotic device, the affected robotic arm can move freely, destroying the ability of the robotic device to remain stationary when electrical and/or hydraulic power is turned off. A submersible is, by design, tightly packed with sensitive and crucial instruments and devices. If a robotic device were to move when turned off, these sensitive and crucial instruments and devices may be damaged. This to is an unacceptable condition and one which requires the actuator to be as nearly leak proof as possible.
Various devices have been aimed at resolving the leakage issue in rotary vane actuator devices with limited success. For example, in U.S. Pat. No. 4,510,850, attempts are made to place a seal between the end walls of the vane and the actuator housing. In this embodiment the vane seals are linear and attempt to match seal length with the seal between the vane seal and actuator housing.
In U.S. Pat. No. 4,495,856, a body sleeve houses a stator and a rotary vane. The rotary vane extends radially from the drive shaft is seals are placed at either end of the drive shaft where it is secured by a pair of head assemblies. The body sleeve includes metal end plates at either end of the head assemblies which are designed to retain tapered, roller thrust bearings within the head assemblies. By tapering, the potential leak path becomes narrower and then can be filled with sealing materials. However, the machining and consequently manufacturing costs may be quite high and even prohibitive for providing this type of arrangement.
In U.S. Pat. No. 4,565,119, there is disclosed a vane-type rotary actuator employing a disc like seal member made of an elastic material with a center opening. The vanes here appear to use one or more elastomeric O-rings to make continuous contact with the with a cylinder. However, this disclosure does appear not address the potential leak path between the ports or the end plates.
In order to perfect a seal in any of the above devices or any known device, special attention to manufacturing detail may cause the actuator to become so expensive and difficult to manufacture as to be useless. Tolerances required between flat surface seals and a matching of lengths of flat surface seals are difficult if not impossible to accomplish consistently using traditional economically acceptable and known manufacturing techniques.
What is needed is an actuator which lends itself to known manufacturing techniques and provides the actuator with virtually no leak paths. Such an actuator must neither leak internally (port to port) nor externally, chamber to environment. The desired actuator would cost no more to manufacture than known actuators and would add to the effective and efficient operation of the device of which it was a part.
It is an object of this invention to provide a rotary vane actuator device that provides three dimensional sealing whether the actuator is static or dynamic.
It is an additional object of this invention to provide such an actuator device that minimizes the potential leak paths using system sealing assemblies positioned within the chamber of rotation and at least partially external thereto.
It is an additional object of this invention to provide such an actuator device which is manufactured using traditional methods and equipment.
In accordance with the above objects and those that will be mentioned and will become apparent below, the rotary vane actuator device in accordance with this invention comprises:
A rotary vane actuator comprising:
an housing having at least one opening for allowing fluid into and out of the housing:
a first and a second cylindrical end plates
a stator housing between the end plates, the stator housing having with a central opening and when assembled with the end plates defining a chamber, that includes a stator fixedly located on the stator housing [and being in central opening; and
a rotor within the central opening and journaled by the housing for rotational movement of the rotor relative to the stator, the rotor including a vane assembly for facilitating movement of the rotor upon flow of fluid into and out of the chamber; and
a sealing assembly including:
a removable multi-element stator seal pack removably positioned between the first and second members of the stator;
a removable multi-element vane pack that securely fits into the machined depressions of the rotor and a removable multi-element seal assembly; and
each end plate having an end plate seal inside the central opening of the stator housing and between the end plates; and
the rotor, said stator seal pack, rotor seal pack and end plate seals being in mating relationship to each other, thereby preventing fluid bypass from the chamber into the ports or into the environment and wherein upon assembly of the actuator device, at least a portion of the end plate seal is within the chamber.
With the actuator described above, a three dimensional sealing system is provided which seals potential leak paths from port to port, from port to the environment and from the chamber to the environment. Each of these potential leak paths is blocked by at least one of the seals described above.
In a preferred embodiment of the actuator in accordance with the invention, each of the seal packs includes a vane seal and each of the vane seals and the end plate seal are made from a plastic material. Preferably, the vane seals are made from polyurethane and the end plate seal is made from a high strength plastic such as Delrin(copyright) and Kynar(copyright).
In another preferred embodiment, the end plate seals are at least partially within the chamber and fixed from falling into the chamber. Preferably the end plate seal has an open center and is force fit over the rotor and on either side where the end plates fit with the rotor squeezing the end plate therebetween.
It is an advantage of this invention to provide a system of compatible plastic seals which when in contact with one another provides a fluid proof seal.
It is an additional advantage of this invention to provide an actuator, which features end plate seals that are at least partially within the chamber.